In 1976, as the United States was celebrating its bi-centennial year, U.S. Intelligence was monitoring radar and electromagnetic signals from the Soviet Union. What had their attention was a pulsing signal that was being sent at 3.26 and 17.54 megahertz. The pulsing signal modulated at a rate of several times a second, resembling the sound of a Woodpecker. It was soon traced to an enormous transmitter array near Kiev in the Ukraine.
Scridb filter